Antityrosinase activity of Euphorbia characias extracts

Tyrosinase is a well-known key enzyme in melanin biosynthesis and its inhibitors have become increasingly important because of their potential use as hypopigmenting agents. In the present study, the anti-melanogenic effect of aqueous and ethanolic extracts from Euphorbia characias leaves, stems, and flowers in cell-free and cellular systems was examined. All the extracts showed inhibitory effects against mushroom tyrosinase with leaf extracts exhibiting the lowest IC50 values of 24 and 97 µg/mL for aqueous and ethanolic extracts respectively. Enzyme kinetic analysis indicated that leaf aqueous extract acts as a mixed type inhibitor, while ethanolic extract shows a competitive inhibition effect on mushroom tyrosinase using L-DOPA as substrate. In addition, the inhibitory effect of leaf extracts on tyrosinase activity and melanin production was examined in murine melanoma B16F10 cells. Cellular tyrosinase activity as well as levels of melanin synthesis are reduced in a dose-dependent manner by extracts in cells treated with α-melanocyte stimulating hormone (α-MSH). The effects are comparable, and sometimes even better, than that of kojic acid, a well known tyrosinase inhibitor used for reference. All these results suggest that E. characias could be a great source of the natural inhibitors from tyrosinase and has the potential to be used as a whitening agent in therapeutic fields.